Abstract: In order to understand the effect of host insects from cold acclimation with different temperatures on the biological characteristics of entomopathogenic nematodes (EPN),we conducted a laboratory experiment and investigated the mortality,infection rate,reproduction ability and survival rate of EPN to different temperatures acclimation insects.The results showed that Steinernema carpocapsae had no significant influence on the mortality rates for the fifth stage of larva of Amyelois transitella (Walker) acclimatized with four temperatures (10 ℃,15 ℃,20 ℃ and 25 ℃) for 7 days.However,S.feltiae resulted in significantly greater mortality rate for the fifth stage larva with 10 ℃ cold acclimation (96.7%) than that with 25 ℃ acclimation (81.4%).The infection rates of S.carpocapsae and S.feltiae to the insects with 10 ℃ cold acclimation were 49.3% and 39.7%,respectively,significantly greater than those with 25 ℃ acclimation (26% and 24%,respectively).With the decreased temperatures,proportion of host insect with EPN emergence showed an increasing trend and greater increase was found in S.feltiae than that of S.carpocapsae.The reproduction rate of EPNs inside the insects treated with 10 ℃ cold acclimation was greater than that of acclimatized at 25 ℃ and the increasing reproduction rate of S.feltiae was higher than that of S.carpocapsae.The cold acclimation of the host could increase the frozen survival ability of EPN.Acclimation at the fifth stage larva of navel orangeworm at 10 ℃ for 7d was greater in enhancing the virulence,infection,reproduction rate,yield and frozen survival of S.feltiae,than those of S.carpocapsae.